CONTROLS
OPERATING SEQUENCE
Heating — When the thermostat calls for heating, terminal ‘‘W’’
is energized, starting the induced-draft motor. When the hall-
effect sensor on the induced-draft motor senses that it has
reached the required speed, the burner ignition sequence be-
gins. The indoor (evaporator) fan motor (IFM) is energized
45 seconds after flame is established. When the thermostat is
satisfied and ‘‘W’’ is deenergized, the IFM stops after a
45-second time-off delay.
Cooling — When the system thermostat calls for cooling, 24 V
is supplied to the ‘‘Y’’ and ‘‘G’’ terminals of the thermostat. This
completes the circuit to the contactor coil (C) and indoor (evapo-
rator) fan relay (IFR). The normally open contacts of C close
and complete the circuit through compressor motor (COMP) to
outdoor (condenser) fan motor (OFM). Both motors start in-
stantly. The set of normally open contacts of IFR close and com-
plete the circuit through IFM. The IFM starts instantly.
On the loss of the thermostat call for cooling, 24 v is removed
from both the ‘‘Y’’ and ‘‘G’’ terminals (provided the fan switch is
in the ‘‘AUTO’’ position) deenergizing the compressor contactor
and opening the contacts supplying power to compressor/OFM.
After a 30-second delay, the IFM shuts off. If the thermostat
fan selector switch in is the ‘‘ON’’ position, the IFM will run
continuously.
NOTE: On units with a Time GuardT II device: once the com-
pressor has started and then stopped, it cannot be restarted
again until 5 minutes have elapsed.
24
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